The present disclosure relates to emulsion aggregation toners and processes useful in providing color toners suitable for electrostatographic apparatuses, including xerographic apparatuses such as digital, image-on-image, and similar apparatuses.
Numerous processes are within the purview of those skilled in the art for the preparation of toners. Emulsion aggregation (EA) is one such method. These toners are within the purview of those skilled in the art and toners may be formed by aggregating a colorant with a latex polymer formed by emulsion polymerization. For example, U.S. Pat. No. 5,853,943, the disclosure of which is hereby incorporated by reference in its entirety, is directed to a semi-continuous emulsion polymerization process for preparing a latex by first forming a seed polymer. Other examples of emulsion/aggregation/coalescing processes for the preparation of toners are illustrated in U.S. Pat. Nos. 5,403,693, 5,418,108, 5,364,729, and 5,346,797, the disclosures of each of which are hereby incorporated by reference in their entirety. Other processes are disclosed in U.S. Pat. Nos. 5,527,658, 5,585,215, 5,650,255, 5,650,256 and 5,501,935, the disclosures of each of which are hereby incorporated by reference in their entirety.
One type of emulsion aggregation toner includes a styrene acrylate resin as illustrated in, for example, U.S. Pat. No. 6,120,967, the disclosure of which is hereby incorporated by reference in its entirety.
Emulsion aggregation techniques involve the formation of an emulsion latex of the resin particles, which particles have a small size of, for example, from about 5 to about 500 nanometers in diameter, by heating the resin, optionally with solvent if needed, in water, or by making a latex in water using emulsion polymerization. A colorant dispersion, for example a pigment dispersed in water, optionally also with additional resin, may be separately formed. The colorant dispersion is added to the emulsion latex mixture, and an aggregating agent or complexing agent is then added to form aggregated toner particles. The aggregated toner particles are optionally heated to enable coalescence/fusing, thereby achieving aggregated, fused toner particles. This process can lead to poorly dispersed pigment throughout the toner and thus lead to lower density on the image page.
Microencapsulation techniques for dyeing of latex particles are known. One such technique is the emulsification/solvent evaporation method, in which styrene/butyl acrylate monomers are emulsified to create latex particles which are simultaneously impregnated with dye. This method limits control over the particle size and dispersion of the dye. Another known technique incorporates dye into preformed toner particles using a dichloromethane dye solution to plasticize the latex particles and facilitate dye transport, as illustrated in U.S. Pat. No. 4,613,559, the disclosure of which is hereby incorporated by reference in its entirety. In this technique, the particle size and shape are unchanged after dye incorporation; however, harmful organic solvents are used.
Improved methods for producing color toner, which increases the color gamut of an EA toner, improves color dispersion, and is less environmentally harmful, remain desirable.